(1) Field of the Invention
The invention relates to a method of deposition of silicon oxide layers in the fabrication of integrated circuits, and more particularly to a method of oxide deposition resulting in improved uniformity and moisture resistance in the manufacture of integrated circuits.
(2) Description of the Prior Art
In the fabrication of semiconductor integrated circuits, and more specifically those in which silicon is the semiconductor, various uses are made of layers of insulating material. For example, such insulating layers are employed as electrical insulation between conducting layers such as electrical interconnection patterns. Another example is the insulion between the polysilicon gate electrode layers and their various interconnections. Still another example is the use of insulating layers to cover over the circuit structure before final provision of electrical contacts. This latter application is referred to as the passivation layer, For these specific and other applications, use is commonly made of chemically-deposited layers of silicon oxide in which the chemical reaction providing the deposited layer of silicon oxide is often enhanced by an electrical plasma sustained in the reactive gases by a radiofrequency power input.
The silicon oxide layers deposited by plasma-enhanced chemical vapor deposition from silicon-containing gaseous compounds and oxygen afford better coverage over surface topographical features such as steps and edges, but are of inferior quality with respect to etching behaviour and moisture resistance compared to silicon oxide layers obtained from mixtures of silane (SiH4) and oxygen. Such silicon oxide layer properties as etch rate, moisture resistance, and mechanical stress are critical in the fabrication of semiconductor integrated circuit devices, especially with respect to manufacturing yield and device reliability. The method of using vapors consisting of silicon-containing compounds such as tetraethoxysilane in plasma-enhanced chemical vapor deposition processes in conjunction with oxygen to deposit silicon oxide layers is described in "SILICON PROCESSING FOR THE VLSI ERA" by S. Wolf, published by Lattice Press, Sunset Beach, Calif. 1990 p. 194-199, but the quality of such silicon oxide layers is generally not as satisfactory with respect to etch rate, moisture resistance, and mechanical stress as are those obtained from silane and oxygen.